Beam loss and collimation issues at LHC can only be briefly outlined in three pages, but some emphasis is given to the bibliographic material. TABLE 1. Some LHC nominal parameters related to beam losses Luminosity 10 34 cm −2 s −1 Normalised emittence 3.75 µm β * at crossing 0.5 m σ * at crossing 16 µm Bunch population 1.05 10 11 protons Stored bunches 2800 Injection energy 450 Gev Collision energy 7000 Gev Injected intensity 12 × 2.5 10 13 protons Stored intensity 3 10 14 protons Stored energy (per beam) Injection 12 × 2 MJ ≡ 12 × 4 kg melted Cu Collision 304 MJ ≡ 800 kg melted Cu

The problem of collimation and beam cleaning is one of the most challenging aspects of the LHC project. A collimation system must be designed, built, installed and commissioned with parameters that extend the present state-of-the-art by 2-3 orders of magnitude. Problems include robustness, cleaning efficiency, impedance and operational aspects. A strong design effort has been performed at CERN over the last two years. The adopted phased approach is described. Robust and precisely controllable collimators have been designed. Several LHC prototype collimators have been built and tested with the highest beam intensities that are presently available at CERN. The successful beam tests are presented, including beam-based setup procedures, a 2 MJ robustness test and measurements of the collimator-induced impedance. Finally, an outlook is presented on the challenges that are ahead in the coming years. Large Hadron Collider Project AbstractThe problem of collimation and beam cleaning is one of the most challenging aspects of the LHC project. A collimation system must be designed, built, installed and commissioned with parameters that extend the present state-of-the-art by 2-3 orders of magnitude. Problems include robustness, cleaning efficiency, impedance and operational aspects. A strong design effort has been performed at CERN over the last two years. The adopted phased approach is described. Robust and precisely controllable collimators have been designed. Several LHC prototype collimators have been built and tested with the highest beam intensities that are presently available at CERN. The successful beam tests are presented, including beam-based setup procedures, a 2 MJ robustness test and measurements of the collimator-induced impedance. Finally, an outlook is presented on the challenges that are ahead in the coming years.

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The Large Hadron Collider (LHC) will collide proton beams at 14 TeV c.m. with unprecedented stored intensities. The transverse energy density in the beam will be about three orders of magnitude larger than previously handled in the Tevatron or in HERA, if compared at the locations of the betatron collimators. In particular, the population in the beam halo is much above the quench level of the superconducting magnets. Two LHC insertions are dedicated to collimation with the design goals of preventing magnet quenches in regular operation and preventing damage to accelerator components in case of irregular beam loss. We discuss the challenges for designing and building a collimation system that withstands the high power LHC beam and provides the required high cleaning efficiency. Plans for future work are outlined. * Members of CERN-Russia and CERN-Canada Collaborations to the LHC Project Large Hadron Collider Project AbstractThe Large Hadron Collider (LHC) will collide proton beams at 14 TeV c.m. with unprecedented stored intensities. The transverse energy density in the beam will be about three orders of magnitude larger than previously handled in the Tevatron or in HERA, if compared at the locations of the betatron collimators. In particular, the population in the beam halo is much above the quench level of the superconducting magnets. Two LHC insertions are dedicated to collimation with the design goals of preventing magnet quenches in regular operation and preventing damage to accelerator components in case of irregular beam loss. We discuss the challenges for designing and building a collimation system that withstands the high power LHC beam and provides the required high cleaning efficiency. Plans for future work are outlined.

After a short review of past collimation work at LHC, the conception and baseline of the LHC collimation system are described. Abort-gap cleaning and beam loss monitoring are also discussed. Paper presented at the HALO03 ICFA Advanced Beam Dynamic workshop, held at Montauk, USA , May 2003.